In a conventional technique, a horizontal type blind is provided with an obstacle detection stopping device which stops unwinding of a lifting cord to stop lowering of slats and a bottom rail when the bottom rail collides with an obstacle during lowering of the slats; and such an obstacle detection stopping device of a solar radiation shielding apparatus has been disclosed many times. Such obstacle detection stopping device includes a collision detection means which detects that a bottom rail collides with an obstacle and a lowering stopping means which stops unwinding of a lifting cord on the basis of collision of the obstacle with a bottom rail.
An obstacle detection stopping device of a solar radiation shielding apparatus disclosed in a patent document 1 includes springs and a stop ring as a collision detection means; and gears as a lowering stopping means. The collision detection means detects collision with a bottom rail and an obstacle on the basis of slack of a lifting cord; and the lowering stopping means stops lowering of slats and the bottom rail on the basis of the slack of the lifting cord. More specifically, the stop ring is penetrated by the lifting cord and biased by the springs toward the gear direction; and the stop ring moves toward the gear direction by biasing force of the springs so as to be engaged with the gears when the slack is generated in the lifting cord. Then, it is configured that the stop ring is engaged with the gears, whereby unwinding of the lifting cord can be stopped; and the stop ring is engaged with the gears, whereby the lowering of the bottom rail is stopped.    Patent document 1: Japanese Registered Utility Model No. 2546419